1. Field of the Invention
This invention relates to ultrasound therapy devices and more specifically to ultrasound therapy devices capable of functioning in pulsed or continuous modes and having automatic feedback control of transducer power.
2. Description of the Prior Art
Ultrasound therapy medical devices are available which operate in pulsed or continuous modes. In the continuous mode the devices emit an ultrasonic frequency from a transducer which is housed in a hand held applicator. The power supplied by the device to the transducer can be selected by the operator.
The applicator has a generally flat face which is applied against the skin of a patient undergoing treatment. As the operator directs the applicator over the area to be treated, the ultrasonic energy causes the underlying tissue to heat up producing beneficial therapeutic results.
In the pulsed mode, available devices emit the ultrasonic frequency with pulses having either a variable duration or a variable period but not both. In some applications it may be useful to have a high frequency of pulses with a relatively short pulse duration. In other applications, it may be useful to have a low frequency of pulses with a relatively long pulse duration. Also, varying the pulse duration for a given pulse period produces different treatment benefits for the patient. The presently available devices do not provide these functions.
The pulsed mode is used to deliver a higher power to the patient for short repeated intervals than may be desirable during a continuous application. The pulsed mode also allows the blood flow and lymphatic drainage system in the treated tissue of the patient to carry off exudates and other matter in between bursts of ultrasonic energy.
The therapy benefits of ultrasonic energy are dependent not only on a continuous or pulsed mode of application, but also on the level of ultrasonic energy directed to the patient's tissue. This level of energy is dependent on the energy transmitted by the transducer.
As the applicator housed transducer is moved over the patient's skin, the ultrasonic energy is absorbed in fat, bone and muscle tissue. These different types of tissue absorb different amounts of ultrasonic energy and therefore present different load conditions on the transducer.
For a given input voltage to the transducer, under changing load conditions, the output power or energy level of the ultrasonic energy will likewise change. The presently available devices typically supply a constant selected voltage to the transducer despite the load conditions involved. This results in uncertainty as to the actual level of ultrasonic energy being directed to the various portions of the patient's body. More effective treatment may be provided by supplying a known constant energy level of ultrasonic energy to the patient.
Presently available devices do not have any means for monitoring the transducer for various conditions such as open or short circuits, overheating or deterioration. Thus, errors of this type, which may be undetected by the operator and the patient, may result in improper treatment to the patient.
Additionally, presently available devices present output information to the operator in the imprecise form of analog meters, mechanical rotary switches and mechanical timers.